Keywords do not need to be repeated verbatim throughout a piece of content. In a headline, in particular, you want to use a keyword (or keywords) in a way that makes the most sense to your audience. The goal should be to write a stellar headline (somewhere between 4-9 words) that clearly explains what a piece of content is about.
Nothing is more of a buzzkill than having a headline that’s awkwardly framed around one keyword phrase or, worse, that forcibly repeats a keyword phrase. This rule applies not only to headlines, but also the content on the page: the goal should be to inform the reader, not to inform the search engines.
Make sure you do your research regularly as trend can change fast with regards to what keywords people are using to search for things online.
Google's keyword research tool is a great resource to help you find the keywords that are most relevant for your business.